Bellows pump with flexible partition membrane

ABSTRACT

It is sought to provide a small-size and highly safe bellows pump dealing with an explosive gas or the like as pump feed fluid, which can prevent hazards due to reaching of a drive motor or like drive part by the pump feed fluid caused to leak out when the bellows is broken. A flexible partition membrane is stretched between the movable end of the bellows and the pump housing to make the outside-bellows region to be a sealed chamber. The flexible partition membrane can follow the reciprocation of the bellows and does not interfere with the operation thereof. When the pump feed fluid leaks out from the pump chamber due to breakage of the bellows during operation thereof, it is retained in the sealed outside-bellows region, and does not reach the drive part including the drive motor. Also, the flexible partition membrane prevents dust intrusion to the bellows side, thus preventing such troubles as the breakage of the bellows otherwise stemming from the dust intrusion.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to bellows pumps and, more particularly, to a bellows pump, which can solve the problems of leaks of the pump feed fluid due to breakage of the bellows, and is particularly suitable for use as an air pump or the like dealing with explosive gases.

[0003] 2. Description of the Prior Art

[0004] In the case of dealing with, for instance, an explosive gas as pump feed fluid, leakage of the gas to the outside of the bellows due to breakage thereof, is extremely hazardous such as electric spark ignition of the bellows drive motor. Accordingly, heretofore explosion-proof structures as the whole pump inclusive of the motor part have been provided. Also, usually a sensor is provided, which detects a pressure change in the pump chamber due to breakage of the bellows and causes the pump operation to be stopped when a predetermined level is reached by the detected level.

[0005] With the explosion-proof structure as the whole pump, it is possible to evade leakage of the pump feed fluid to the outside of the pump due to breakage of the bellows. However, once the leakage takes place, the whole pump inclusive of the drive motor becomes useless, thus leading to the problems that the pump life is short and that the maintenance expenditures are increased. The adopting of the explosion-proof structure further has the problems of increasing the size of the whole pump head and the expenditures required for the explosion-poof device. Further, by merely providing the leakage detection sensor, it is impossible to prevent the hazard due to already leaked gas or the like.

[0006] The present invention was made in view of the above problems inherent in the prior art, and its object is to provide a bellows pump, which can reliable prevent, when the pump feed fluid leaks out due to breakage of the bellows, the intrusion of the leaking fluid into hazard localities such as the drive motor, permits its life time increase, facilitates its maintenance and is low in cost, highly safe and small in size.

SUMMARY OF THE INVENTION

[0007] To attain this object, the present invention intends to provide a bellows pump, which has a structure comprising a pump head having an intake and a discharge port for passing pump feed fluid therethrough, a cylindrical pump housing secured to the pump head, a bellows capable of being elongated and contracted, which is accommodated in the pump housing to define a pump chamber therein, and has a secured end communicating with the intake and discharge ports of the pump head via uni-directional valves, respectively, and a movable end capable of being reciprocated in the pump operation, and a bellows drive means coupled via the movable end of the bellows to a crank mechanism and serving to cause reciprocation of the bellows in the pump operation, wherein a flexible partition membrane is stretched between the movable end of the bellows and the housing and capable of following the reciprocation of the movable end, and an outside-bellows region defined on the outside of the bellows between the bellows and the housing is made to be a sealed chamber.

[0008] With this structure of the bellows pump according to the present invention, when the pump feed fluid in the bellows leads out due to breakage thereof, it is stained in the sealed chamber defined by the flexible partition membrane, thus preventing the leaks over the entire pump, and particularly it is possible to reliably prevent intrusion into the bellows drive part which is subject to spark generation. It is thus necessary only to replace the broken bellows for the duty service operation of the pump afresh. The structure is also desired in view of the maintenance and safety.

[0009] In the specific proposed structure according to the present invention, a volume limiting member is disposed in the pump chamber for limiting the pump chamber volume of the bellows pump, a retainer is mounted on the movable end of the bellows for holding the volume limiting member, and the flexible partition membrane has one peripheral end part clamped between the retainer and the movable end of the bellows.

[0010] With this structure, one peripheral end part of the flexible partition membrane, can be mounted on the movable end of the bellows by using the retainer and thus without need of any separate mounting means.

[0011] According to the present invention, it is further proposed to adopt a diaphragm as the flexible partition membrane. Since the material of the diaphragm is used for the reciprocal part of pump in the diaphragm pump, it can withstand use for longer time than the bellows, and it is thus desired for constituting the sealed chamber.

[0012] Furthermore, the bellows pump according to the present invention provides for high safety as an airpumpparticularlydealing with an explosive gas or the like as the pump feed fluid.

[0013] As in the above, with a bellows pump according to the present invention the outside-bellows region is made to be a sealed chamber by stretching the flexible partition membrane between the movable end of the bellows and the housing. Thus, when the pump feed fluid leaks out of the pump chamber to the outside of the bellows due to breakage of the bellows caused during the pump operation, it is retained in the sealed chamber and does not reach the drive part such as the drive motor at all. Thus, in the case of use as air pump dealing with an explosive gas, it is possible to eliminate such hazards as gas leakage and also dispense with any explosion-proof mechanism for protecting the entire pump. This means that it is readily possible to realize pump size reduction. In the maintenance, it is necessary only to replace the sole broken bellows, thus saving otherwise necessaryexpenditures. The flexiblepartitionmembranecan further prevent external dust intrusion into the bellows side to prevent consequent breakage of the bellows. Thus, it is possible to provide a bellows, which is small in size, highly safe and capable of being used for long time.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will become more apparent upon a reading of the following detailed specification with reference to the accompanying drawings, in which:

[0015]FIG. 1 is a longitudinal sectional view showing an embodiment of the bellows pump according to the present invention; and

[0016]FIG. 2 is a transversal sectional view taken along line A-A in FIG. 1 showing a planar flexible partition membrane.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0017] An embodiment of the bellows pump according to the present invention will nowbe describedwith reference to the drawings. FIG. 1 shows a pump head 1 having an intake and a discharge port 2 and 3 allowing a pump feed fluid to pass therethrough. The pump head 1 also has uni-directional valves 4 a and 4 b disposed at the intake and discharge ports 2 and 3, respectively. A valve case 5 as a constituent part of the pump head 1, supports the uni-directional valves 4 a and 4 b. The uni-directional valve 4 a disposed at the intake port 2 allows in-flow of the pump feed fluid from the intake port 2, and blocks the flow in the converse direction. The uni-directional valve 4 b disposed at the discharge port 3 allows out-flow of the pump feed fluid from the discharge port 3, and blocks the flow in the converse direction.

[0018] A cylindrical pump housing 6 has one end secured in a sealed state via a gasket 7 to the valve case 5 constituting part of the pump head 1. A bellows 8 is disposed in the housing such that it undergoes elongation and contraction in the longitudinal axis line X-X of the pump with deformation of its bellows part. One end (i.e., secured end) 8 a of the bellows 8 is secured via a split flange 9 to the pump head 1. The flange 9 is set on an inner peripheral shoulder of the pump housing 6 formed at one end thereof. The secured end 8 a of the bellows 8 and the pump head 1 are sealed by a gasket 10 to each other. The above various constituting parts of the pump are secured to one another in a mutually clamped state by bolts 25, which are inserted through the pump head 1 up to the opposite end coupler frame 24 along the axis line X-X.

[0019] The bellows 8 has its inner space defined as a pump chamber 11, which the intake and discharge ports 2 and 3 are communicated with via the uni-directional valves 4 a and 4 b, respectively, and through the secured end Ba of the bellows 8. The pump operation is such that as the bellows 8 is reciprocated along the axis line X-X, the pump feed fluid is caused to flow from the intake port 2 via the uni-directional valve 4 a to the pump chamber 11, and is also caused to flow out via the other uni-directional valve 4 b from the discharge port 3 to an external necessary locality.

[0020] As the pump feed fluid, an explosive gas, for instance, is dealt with. In this case, the pump constitutes an air pump. However, it is also possible to deal with a chemical or like liquid as the pump feed fluid, and the pump is not limited to the air pump.

[0021] The other end (i.e., movable end) 8 b of the bellows 8, which is reciprocated in the pump operation, is coupled via a crank mechanism including a connecting rod 12 and an eccentric shaft 13 to a drive motor 14. The drive torque of the drive motor 14 is transmitted from the motor shaft 15 via the eccentric shaft 13 to the connecting rod 12 to be converted to reciprocal motion of the connecting rod 12. The reciprocal motion is transmitted to the movable end 8 b of the bellows 8. The drive motor 14 and the motor shaft 15 together constitute a bellows drive means for causing pump operation of the bellows 8 via the eccentric shaft 13 and the connecting rod 12 constituting the crank mechanism. The eccentric shaft 13 has one end secured by a key 16 to the motor shaft 15, the other end rotatably supported via a bearing 17 in a drive motor frame 18, and an intermediate eccentric shaft part 13 a operatively coupled via a bearing 19 to one end of the connecting rod 12.

[0022] The other end of the connecting rod 12 is screwedly made integral with and coupled to a retainer 20 mounted on the movable end 8 b of the bellows 8. The retainer 20 holds a volume limiting member 21, which is located in the pump chamber 23 and serves to limit the volume of the pump chamber defined inside the bellows 8, in a state that the member 21 is screwedly mounted on the movable end 8 a of the bellows 8. The volume limiting member 21 is provided for increasing the changes in volume of the pump chamber 11 in the bellows 8, and hence increasing the pump efficiency, in the pump operation, thus solving a problem of so-called dead space in the pump chamber 11.

[0023] A flexible partition membrane 22 is stretched between the movable end 8 b of the bellows 8 and the pump housing 6. As shown in FIG. 2, the flexible partition membrane 22 has a disc-like shape, and it is made from rubber or a flexible synthetic resin material.

[0024] As shown in FIG. 1, the flexible partition membrane 22 has its inner peripheral part 22 a sealedly mounted on the movable end 8 b of the bellows such as to be clamped between the retainer 20 and the movable end 8 b. The use of the retainer 20 thus dispenses with any separate mounting means. The outer peripheral part 22 b of the flexible partition membrane 22 has an integral flange-like seal rib, which is sealedly secured in position to the pump housing 6 and the coupler frame 24. The flexible partition membrane 22 is mounted in this way.

[0025] By the stretching of the flexible partition membrane 22, the region defined outside the bellows 8 between the bellows 8 and the pump housing 6, i.e., an outside-bellows region 23, is made to be a sealed chamber. Thus, when the pump feed fluid leaks out from the pump chamber 11 to the outside-bellows region 23 due to a damage caused to the bellows 8 during the pump operation, it is retained in the sealed chamber 23 and thus prevented from leaking out to the outside of the sealed chamber 23.

[0026] On its side of the secured end 8 a of the bellows, on which the pump head 1 is located, the outside-bellows region 23 is sealed by the gaskets 7 and 10, while on the side of the movable end 8 b of the bellows it is sealed by the flexible partition membrane 22. Thus, the outside-bellows region 23 is constituted as the completely sealed chamber. The flexible partition membrane 22 is capable of being deformed by following the reciprocation of the movable end 8 b of the bellows, and thus it does not interfere with the operation of the movable end.

[0027] As noted before, the flexible partition membrane 22 is made from rubber or a soft synthetic resin material, and particularly it is preferably constituted by a diaphragm. The diaphragm can withstand use for long time compared to the bellows, and it is thus desirable for constituting a sealed chamber. As for the shape, as shown in FIG. 1, the flexible partition membrane 22 desirably has its peripherally intermediate part formed with an integral annular groove 22 c. By providing the annular groove 22 c, at the time of deformation of the flexible partition membrane 22 redundancy is provided to reduce the degree of resistance offered to the reciprocation of the movable end 8 b of the bellows 8, thus guaranteeing much smoother pump operation.

[0028] It will thus be seen that when the pump feed fluid leaks into the outside-bellows region 22 due to breakage of the bellows 8, it is retained in this sealed region 23 owing to the stretching of the flexible partition membrane 22, and is blocked from the side of the drive part including the drive motor 14 and reliably prevented from reaching this locality. Thus, even in the case of dealing with an explosive gas as the pump feed fluid, it is possible to prevent such hazard that the gas is ignited by a spark generated by mechanical friction around the drive motor. It is thus possible to secure necessary safety without providing any explosion-proof structure as the entirety of the pump. Furthermore, for the maintenance it is necessary only to replace the broken bellows, and the other constituting parts including the drive motor can be directly used as such.

[0029] Moreover, by the provision of the flexible partition membrane 22, it is possible to prevent external dust intrusion into the part of the bellows 8. It is thus possible to perfectly eliminate the possibility of breakage of the bellows that may otherwise be caused by catching of foreign particles in the bellows part of the bellows. In this point again, safety improvement is obtainable.

[0030] The breakage of the bellows 8 can be detected by monitoring the pump chamber pressure with an appropriate pressure sensor (not shown). In other words, a pressure fall can be detected, which is generated expansion of the pump chamber volume inclusive of the sealed chamber due to a breakage of the bellows. The breakage of the bellows is detectable by disposing a flow path sensor (not shown) in the discharge side duct and detecting the stoppage of the flow-out of the fluid to the discharge side due to reduction of the volume ratio in the inside of the pump chamber below a predetermined value due to the breakage of the bellows.

[0031] While in the foregoing a preferred embodiment of the bellows pump according to the present invention has been described, it is by no means limitative. The bellows pump according to the present invention is suitable for use as air pumps dealing with explosive gases with the possibility of explosion, but the present invention is also likewise applicable to pumps dealing with general gases or chemical liquids. The flexible partition membrane is suitably a diaphragm, but other flexible membrane-like parts may be used as well. 

What is claimed is:
 1. A bellows pump comprising: a pump head having an intake and a discharge port for passing pump feed fluid therethrough; a cylindrical pump housing secured to the pump head; a bellows capable of being elongated and contracted, which is accommodated in the pump housing to define a pump chamber therein, and has a secured end communicating the intake and discharge ports of the pump head via uni-directional valves, respectively, and a movable end capable of being reciprocated in a pump operation; bellows drive means coupled via the movable end of the bellows to a crank mechanism and serving to cause reciprocation of the bellows in the pump operation; a flexible partition membrane stretched between the movable end of the bellows and the housing and capable of following the reciprocation of the movable end; and a sealed chamber formed in an outside-bellows region defined on the outside of the bellows between the bellows and the housing.
 2. The bellows pump according to claim 1, which further comprises: a volume limiting member disposed in the pump chamber for limiting the pump chamber volume of the bellows pump; and a retainer mounted on the movable end of the bellows for holding the volume limiting member; said flexible partition membrane having one peripheral end part clamped between the retainer and the movable end of the bellows.
 3. The bellows pump according to claim 2, wherein said flexible partition membrane is constituted by a diaphragm.
 4. The bellows pump according to claim 3, which is an air pump for pumping such gas as explosive gases as the pump feed fluid. 